This invention relates to a primary film forming resin for nail lacquers and nail enamel formulations and more particularly is directed to a grafted polymeric film forming resin for nail polish which will function as a replacement for nitrocellulose.
Nail lacquers and enamels typically contain several ingredients among which are a primary film former, secondary film formers, plasticizers, solvents, colorants, and fillers. In the past, nitrocellulose has been the primary film former employed in the majority of nail polish formulations but it suffers from the disadvantages that it is explosive; it tends to discolor as a function of time rendering it aesthetically displeasing; and it is prone to undergo sharp changes in viscosity which make application difficult. Thus a need exists in the nail lacquer arts for an improved primary film forming material.
Unlike copolymers having a linear arrangement of sequences such as -AAABBB- and -ABABAB-, graft copolymers are polymers in which the molecules are characterized by a main backbone chain to which side chains containing different atomic constituents are attached at various points along the main chain. For example a graft copolymer can be represented by the structure ##STR1## The monomer units A and B are referred to as the main chain or backbone, the sequence of C units is the side chain or graft, and X is the unit in the backbone to which the graft is attached.
Nail lacquers containing graft copolymers are not new. For example, in U.S. Pat. No. 5,153,268 issued Oct. 6, 1992, there is described a nail lacquer formulation containing as the film forming resin a graft copolymer having a main backbone chain of acrylic ester monomer units and methacrylic ester monomer units. Grafted to the main backbone chain are side chain units of carboxyl groups and side chain units of trialkoxysilyl groups.
The present invention is an improvement in graft copolymers and nail lacquers in accordance with the '268 patent. Accordingly, in the present invention ethylene glycol dimethacrylate side chain units are grafted to the main backbone chain instead of carboxyl groups, and the resulting graft copolymer is cold blended with a silsesquioxane resin. The blended material is useful as a film forming resin in nail lacquer applications. It possesses improved chip resistance, wearability, hardness, and gloss. The graft copolymer provides improved adhesion and the silsesquioxane resin provides improved hardness for the nail lacquer system.
In an alternate embodiment of the invention, improved nail lacquer film forming resins are obtained by grafting to the main backbone chain, in addition to the trialkoxysilyl groups, side chain units of vinylbenzyl chloride, instead of carboxyl groups as in the '268 patent. Such film forming resins in accordance with this alternate embodiment have been found to possess significantly better adhesion characteristics than the carboxyl group containing film forming resins of the '268 patent.